For many people who use swimming pools for lap swimming, swimming training or learning to swim, a device such as a floating kickboard is used to hold in front of the body to allow the isolation of the upper body so the person can propel themself through the water by kicking the legs only. These kickboards are usually square and cumbersome and non-hydrodynamically shaped.
Swimmers also use a peanut-shaped floating device to place between their thighs which isolates their legs allowing the user to concentrate on arm stroke correction. These devices can be uncomfortable and sharp or small and non-floating.